DECLARATION 2 PUBLICATIONS
6.2 SHAP ABSTRACT OBJECT TESTS
6.2.1 SHAP TEST RESULTS
Video analysis of the SHAP Abstract object tests is shown in the following headings and it gives a graphic of the object moved over the distance of 8 cm. From these images one can grasp the level of difficulty of the grip and how well the hand was able to complete the task.
6.2.1.1 Mechatronic SHAP abstract object test
Figures 6-17 to 6-22 show the video images of the mechatronic hand undergoing SHAP tests.
The results are analysed in terms of the performance of the hand in the tests.
One can see the mechatronic hand performing the spherical grip, picking up a tennis ball in Figure 6-17.
Figure 6-17. Spherical grip - mechatronic hand.
In Figure 6-18 one can see the mechatronic hand performing the cylindrical grip picking up a bottle with ease.
Figure 6-18. Cylindrical grip -mechatronic hand.
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Figure 6-19 shows the mechatronic hand picking up and placing a pen using the tripod grip.
Figure 6-19. Tripod grip - mechatronic hand.
Figure 6-20 shows the mechatronic hand using a lateral grip to pick up and place a small box.
Figure 6-20. Lateral grip - mechatronic hand.
Figure 6-21 shows the mechatronic hand performing the tip grip picking up and placing a small spring using the index and thumb fingers.
Figure 6-21. Tip grip - mechatronic hand.
The extension grip was carried out with the mechatronic hand where the fingers are kept in extension, applying minimal pressure closing. The object is kept between the extended fingers and the thumb as it is moved from one position to another.
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Figure 6-22. Extension grip - mechatronic hand.
In Table 6-6 the results of the SHAP tests for the mechatronic hand are shown with the hand being able to pick up all the objects, the tip grip was the longest to complete at 13 seconds as the spring object used was more difficult for this hand to grasp. All tasks were a success this time showing that the mechatronic version of the hand had strong potential for gripping and manipulating simple fairly lightweight everyday objects.
Table 6-6. Mechatronic hand SHAP abstract object test results.
Grip Success/Fail Time (s)
Spherical Success 9,36
Tripod Success 9,96
Power Success 11,35
Lateral Success 7,56
Tip Success 13,31
Extension Success 10,25
6.2.1.2 Mechanical SHAP abstract object test
SHAP abstract object tests were carried out for the mechanical hand for the same objects.
In Figure 6-23 one can see the mechanical hand picking up a tennis ball, the fingers close well around the ball and this is an example of a spherical grip. There is no trouble picking up and placing the tennis ball, the ball was not dropped during the movement.
Figure 6-23. Spherical grip - mechanical hand.
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In Figure 6-24 one can see the mechanical hand performing a grip similar to the lateral grip on a small box. The hand is able to move the box from one position to another fairly easily and without any problem.
Figure 6-24. Lateral grip - mechanical hand.
The tripod grip is a grip in which the object is held between the index and middle fingers and the thumb. This grip is usually used in holding a pencil. In Figure 6-25 the grip is illustrated with the mechanical hand picking up a pen.
Figure 6-25. Tripod grip - mechanical hand.
The tip grip is a grip that is a grip an object between the index finger and the thumb and is used to pick up fine objects. In Figure 6-26 one can see the mechanical hand picking up a small spring using the tip grip.
Figure 6-26. Tip grip - mechanical hand.
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Figure 6-27 shows the mechanical hand using the power grip which is a grip where an object is clamped between the fingers and the palm, the mechanical hand handles this grip.
Figure 6-27. Power grip - mechanical hand.
A test was carried out using the mechanical hand performing the extension grip. The box was too heavy and kept slipping from the hands grip, so the mechanical hand failed this grip type.
Table 6-7 shows the results of the mechanical hand SHAP tests on abstract objects. The hand performed fairly well and was able to pick up most objects, the only failure being the extension grip, this was the heaviest weight and also one of the more difficult grips. The times here are shown and one can see that the hand closes quickly enough to allow for grasping, the tripod grip took the longest with the delay being in grasping the object.
Table 6-7. Mechanical hand SHAP abstract object test results.
Grip Success/Fail Time (s)
Spherical Success 7,42
Tripod Success 16,51
Power Success 9,03
Lateral Success 7,2
Tip Success 7
Extension Fail >20
From the video analysis one can see that the mechanical and mechatronic hands can both perform similar grip patterns with the only grip that wasn’t carried out being the failure of the mechanical hand to perform the extension grip. This was after a few attempts, and can be due to the weight and shape of the object being difficult to grip. Also the spring tension force in the hand can be a detractor to its performance for picking up all objects.
The mechatronic hand on the other hand had good success with picking up all the objects as can be seen in the Figure 6-28. One notable difference between the mechanical and mechatronic hand was the time taken for the hands to grip the objects with the mechatronic hands time being noticeably longer. The delay time for the motors to close was set at 4 seconds in programming the fingers motors closing. This was done as four seconds gave enough time to allow for manipulating the hand to grasp the objects.
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The SHAP Abstract object tests are known to give a good representation of hand performance in common activities of daily living (ADL’s).The assessment has been shown to be a statistically reliable measure of hand functionality and thus gives a good assessment of both hands designed here. (Skyler A. D., 2012). A comparison of the times taken to perform the various tasks can be seen below, with the advantage in most cases being slightly with the mechanical hand, except for two occurrences.
Figure 6-28 is a bar graph showing a comparison of the times taken to perform different grasps, it gives a good visual comparison of the differences between the two types of hand tested.
Figure 6-28. Comparison between hands: SHAP abstract object tests.
SHAP was designed to be used with all hands - natural, impaired or prosthetic and emphasises the function of the hand. (Kyberd, P. J., 2017). In this dissertation one has looked at the more basic aspects of the SHAP Abstract object test - i.e. Is the hand able to perform a specific task and how long does it take to perform that task.